Hubble bubble (astronomy)

In astronomy, a Hubble bubble would be "a departure of the local value of the Hubble constant from its globally averaged value", or, more technically, "a local monopole in the peculiar velocity field, perhaps caused by a local void in the mass density". The Hubble constant, named for astronomer Edwin Hubble, whose work made clear the expansion of the universe, measures the rate at which expansion occurs.

Source: Wikipedia — Hubble bubble (astronomy) (CC BY-SA 4.0)